1. Field of the Invention
The present invention relates to an image processing apparatus, and more particularly, to an image processing apparatus and method for performing an image combination process using a plurality of images and a program for allowing a computer to execute the method.
2. Description of the Related Art
In recent years, imaging apparatuses such as digital still cameras or digital video cameras (for example, camcorders) that image a subject such as a person or an animal to generate image data and record the image data as image content have been popularized. Moreover, imaging apparatuses that generate an appropriate captured image by automatically performing appropriate exposure control in accordance with a subject have been proposed.
Here, when an imaging operation is performed with exposure control with respect to a scene (for example, a backlit scene) with a large difference in luminance, it is expected that the imaging device provided in an imaging apparatus has an insufficient dynamic range. When the dynamic range of the imaging device is not sufficient, a whiteout may occur in a saturated bright area of a captured image, or a blackout may occur in a dark area of the captured image.
Therefore, an imaging apparatus that generates a combined image with a wide dynamic range by combining a long exposure image and a short exposure image which are generated by an imaging process with different exposure periods has been proposed. However, when a moving object is included in the combination target images used at the time of generating the combined image, there is a possibility that a combined image including the moving objects before and after the movement is generated and appears unnatural (so-called multiple exposure).
Therefore, an imaging apparatus that calculates a difference between a long exposure image and a short exposure image obtained by multiplying it by an exposure ratio between the long exposure image and the short exposure image and switches the images used for generating a combined image in accordance with whether the difference exceeds a predetermined level is proposed (for example, see FIG. 3 of JP-A-2002-101347). In this imaging apparatus, for example, when the difference exceeds a predetermined level, it is determined that there is an image shift between the short exposure image and the long exposure image, and the combination target images are switched in accordance with the polarity of the difference.